Fuse plug



p 1936 F. e. LEAVENWORTH 2,@55,35

FUSE PLUG Filed Jan. 10, 1955 Patented Sept. 22, 1936 UNITED STATES PATENT OFFICE FUSE PLUG Application January 10, 1935, Serial No. 1,111

2 Claims. (Cl. 200-113) The invention relates to fuse plugs, and one of its objects is to provide an improved fuse plug which includes a liquid which will be blown out of bridging relation between the terminals when an overload is placed on the circuit. Another object of the invention is to provide a fuse plug of the liquid type which, by movement or manipulation of the plug orbody in which liquid is contained, can be readily restored to bridging relation between the terminals for reuse.

The invention consists in the several novel features which are hereinafter set forth and are more particularly defined by claims at the conclusion hereof.

In the drawing which accompanies and forms a part of this specification or disclosure and in which like numerals of reference denote corresponding parts throughout the several views:

Fig. 1 is a perspective of a fuse embodying the invention. Fig. 2 is a longitudinal section. Fig. 3 is a transverse section on the line 33 of Fig. 2. Fig. 4 is a transverse section on the line 4-4 of Fig. 2.

The fuse plug which forms the subject matter of the invention is adapted to be inserted in an ordinary screw socket and comprises a hollow body or base 6 of insulating material. It also comprises a screw-shell l which fits around and is secured to the periphery of the body and is adapted to engage the screw in an ordinary horizontally extending socket in a fuse box. A terminal stud 8 isfixed in the integral end 9 of the body 6, and an insert member ID of insulating material is cemented in the hollow body 6 and closes the outer end of the chamber in the body. The screw shell .1 forms the second terminal. A terminal-forming plate or disk H is mounted in the hollow base and is spaced from the terminal 8. Plate H is electrically connected by a wire l2 to the screw shell 1 and is supported in a member I3 of insulating material which is fixedly secured in the body 6 between end 9 and the insert l0. An annular space or chamber i4 is formed in member l3 between the adjacent ends of plate 8 and terminal II and is adapted to retain a measured quantity of liquid l5, such as mercury, to form a fuse or fusible conductor between terminals 8 and H. The inner end of insert I0 is formed with a recess l6 around terminal II and the latter is provided with a central opening ll. The current in the electric circuit passes from the terminal 8 across the liquid l5 to terminal H and through wire I! to the screw terminal 1. Upon an overload in the circuit, excessive flow of current through the fluid in chamber M will blow the liquid'l5 out of said chamber through opening l1 into recess IS. The blown out liquid l5 will then be removed from chamber I4 so that it no longer connects terminals 8 and II, and the circuit through the plug will be interrupted. From recess I6 the blown out fluid will pass into the lower portion of a chamber l8 around the member l3. Member I3 is provided with a pocket or bucket l9 which communicates with a radial port 20 which leads to a duct 2| for delivering the fluid into chamber I4. Rotation of the plug in one direction will cause the pocket I9, when it traverses the mercury at the bottom, to flll with and pick up a measured quantity of mercury and when the pocket approaches the top of the plug, the mercury will flow from the pocket l9 through port 20 and duct 2| into chamber M, where it will again act as a fuse between terminals 8 and ll.

For heavy duty fuses, the mercury is submerged in a quantity of carbon tetrachloride, indicated at 22, to prevent burning of the mercury and the contacts by excluding oxygen and reducing combustion. This carbon tetrachloride also serves quickly to condense the vapor produced by blowing the fuse after it is blown out of chamber M. In some instances, however, this carbon tetrachloride may be dispensed with.

While the plug is being turned into a socket in a fuse box, the member l3 will scoop a measured quantity of the mercury or liquid from the lower portion of chamber l8 and deliver it through port 20 and duct 2| into the chamber l4, wherein the mercury will be retained to serve as a fuse or fusible connection between terminals 8 and II. When the circuit is overloaded, the mercury or liquid between said terminals will be blown through opening I! into recess it. The mercury will be condensed in said chamber and flow into the lower portion of the chamber l8 in readiness for displacement into chamber M for reuse. When the fuse has blown, in order to restore the mercury to chamber M for reuse, it is only necessary to unscrew the plug from its socket approximately a full turn and then turn the plug back into the socket. The turning of the plug into the socket will automatically cause the pocket l9 to scoop the condensed mercury from the lower portion of chamber I8 and carry it to the upper portion of the plug where it will be discharged through port 20 and duct 2| into chamber l4 so it will again form a fuse between terminals 8 and H. Chamber i4 is of such depth ,that it will retain the desired quantity of mercury according 5 to the desired ampere capacity of conductivity, below opening I I, through which any excess of mercury delivered into said chamber will overflow to recess It and thence to the bottom or chamber it. During rotation of the plug aiter chamber II has received a charge of mercury, the annular shape of said chamber will cause the desired quantity of mercury to be retained between terminals 8 and II until it is again blown out.

The invention exemplifies a fuse plug comprising a liquid fuse which is adapted to be blown out of place and which can be readily delivered back into operative position by the manipulation or turning of the plug itself for reuse.

The invention is not to be understood as restricted to the details set forth, since these may be modified within the scope oi the appended claims, without departing from the spirit and scope of the invention.

Having thus described the invention, what I claim as new and desire to secure by Letters Patent is:

1. As a new article of manufacture, a fuse plug adapted for insertion in a horizontally extending electric screw socket and comprising a body consisting of a continuous side wall and an inner end wall of insulating material and having an open ended chamber defined by said side and end walls and a closure member of insulating material disposed in and serving to close the open end of the chamber, a terminal extending through the central portion of the end wall of the body, a screw shell extending around the side wall of the body and adapted to interfit with the screw thread of the electric socket, a terminal disposed in the chamber in spaced relation with respect to the first mentioned terminal and connected to the shell, a member of insulating material disposed in the chamber between the two terminals and having a compartment for retaining a quantity of iuse forming liquid in bridged relation with respect to the two terminals and also having an opening leading from the compartment for permitting the liquid to be blown therefrom into the chamber in the body when an overload is placed upon the plug, and means associated with said member adapted in response to rotation of the body to scoop the blown out liquid from the chamber and deliver it to the compartment to again establish electrical connection between'the two terminals.

2. As a new article of manufacture, a iuse plug adapted for insertion in a horizontally extending electric screw socket and comprising a body consisting of a continuous side wall and an inner end wall of insulating material and having an open ended chamber defined by said side and end walls and a closure member of insulating material disposed in and serving to close the open end of the chamber, a terminal extending through the central portion of the end wall of the body, a screw shell extending around the side wall of the body and adapted to interfit with the screw thread of the electric socket, a terminal disposed in the chamber in spaced relation with respect to the first mentioned terminal and connected to the shell, a member of insulating material disposed in the chamber between the two terminals and having an annular compartment extending transversely of the plug iorretaining a quantity oi fuse forming liquid in bridged relation with respect, to the two terminals and also having an opening leading from the center of the compartment for permitting the liquid to be blown from the compartment into the chamber when an overload is placed upon the plug, and a scoop formed integrally with the member and adapted in response to rotation of the body to scoop the blownout liquid from the chamber and deliver it back to the compartment to establish electrical connection between the two terminals.

FRANK G. LEAVENWORTH. 

